Digging deep excavations, such as cross-country ditches necessitates that a considerable amount of material be removed from the ground in order to provide a ditch bottom which is constructed at a specific elevation or grade. Construction of deep ditches and other excavations usually requires a machine having a ladder type digging apparatus that translocates excavated material from the ditch using a lower run of the digging member, up through a throat and then along a lateral conveyor to a location spaced from the excavating machine. Typically, such excavating machines include a boom carrying a digging chain. The chain is driven by a sprocket located near or on the inner end of the boom, and may be in sliding engagement with one or both surfaces of the boom.
A portion of the digging chain, during a digging operation, comes in contact with surfaces of the boom, causing excessive wear on the boom. To accept wear caused by the friction associated with the digging chain, wear plates have been arranged on the boom. The ware plates are usually installed on the underside of the boom and are illustrated in U.S. Pat. Nos. 4,223,462 and 5,471,771.
Booms also experience excessive wear on the top boom surface adjacent to the inner end of the boom. The transition of the chain from the sprocket at the inner end of the boom, to the boom top surface creates a high wear area at the inner end of the boom top surface. Additionally, in this area, slack is introduced into the chain, and the chain impacts the top surface of the boom resulting in considerable "popping sound" noise being generated. A need has thus arisen for structure to improve the transition of a digging chain at the inner end of a boom as the chain rotates off of the driving sprocket.